Warm Winters, Not so Rare Anymore

I spent a few hours yesterday afternoon at the Arctic Science Summit. This big, international conference has close to 1000 participants made up of scientists and policy makers from across the arctic countries. I’ll be there again today, tweeting about the sessions, and hopefully reporting back some more here. Today, I was drawn to a talk about the weird weather of of the past winter. It was given by Rick Thoman, an Alaska-based meteorologist from the National Weather Service.

If you live in Alaska, you know this winter was a bit strange. It’s been warm. Really, really warm. Ridiculously warm. For the state as a whole, this has been the second warmest winter on record (warmest ever was 2000-2001). There are parts of the state however, notably the Alaska Peninsula and the NW coast of the Gulf of Alaska, that have seen the warmest temps ever. The lowest temperature documented in the state this winter was -47F in the southern Brooks Range village of Arctic Village. That sounds cold, but it’s a whopping 6 degrees warmer than the previous warmest low. With just weeks left in the winter, that statistic is unlikely to change. “This is by far the warmest minimum temperature in a century,” said Rick Thoman.

Here are some more facts:

It’s been dry. Between 1 Dec and 13 March there was no accumulation of snow in the interior (we got a few inches over the past couple of days).

Of the 92 days of winter thus far, 61 have been “above normal”

Bristol Bay has no ice.

By the end of winter there may be the lowest annual maximum of sea ice EVER in the Bering Sea.

North of 80 degrees, the true arctic, every single day since Sept has been above normal.

Fascinating, and more than a little scary.

Even this skim of snow on the mud flats of Turnagin Arm near Anchorage has been a rare sight this year.

It’s easy to point at that string of data and shout about climate change. And make no doubt, what we are seeing is a definite symptom of a changing climate. But there is more to it than that. And if we dig much into the warm winter, we reach into the fuzzy realm between weather and climate.

This season, in addition to steadily warming temperatures over the past century, we also saw a series of other factors come together. As Rick Thoman of the National Weather Service, Alaska said, in 2015-2016, the “Stars alligned.” That constellation includes factors like the persistence of North Pacific “blob”, a warm mass of water lingering off Alaska’s coast, an extremely strong Southern Pacific Oscillation (El Nino), a series of warm pulses of air from the Atlantic, and low ice coverage across the arctic (which is ironically both a symptom and a cause of the abnormally warm temperatures).

It’s a bunch of factors, clearly, that has led to this particularly warm year. But the long term trends have been leading us to this point for many years.

Despite the warm temperatures, snow packs are not far below the average.

If this past winter was unique, a pretty little anecdote to point to and say “Wow, wasn’t that a strange winter” we could move on right now. We can’t. This winter was not “normal” but then, we haven’t had many normal winters since the late 1970s. In fact, since those years, only two winters in Alaska have seen below average temperatures, while close to two thirds of the rest have fallen into the “above normal” range.

The impacts of singularly warm years, such as this one, can be devastating for wildlife. In a previous post, I wrote about the mass die-off of Common Murres. While that die-off is likely the result of the warm water “blob” loitering in the North Pacific, that feature will probably grow more frequent as the arctic and the rest of Alaska get warmer. Other species too are impacted by climate change and these whacky-weather years. The more frequent they become, the more impacts we are likely to see.